KR100936447B1 - Silica-based Photocatalyst Fiber Having Visible-light Activity And Process For The Production Thereof - Google Patents

Abstract

A composite oxide phase comprising an oxide phase (first phase) and a titania phase (second phase) mainly composed of a silica component, wherein the second phase contains a metal element other than titanium, and the second phase A silica-based photocatalyst fiber having visible light activity in which the abundance is increased obliquely toward the surface of the fiber and a method for producing the same.

Silica-based photocatalyst fibers, visible light activity, gradient composition

Description

Silica-based Photocatalyst Fiber Having Visible-light Activity And Process For The Production Thereof}             

1 is a view showing the production process of the oxide fiber of the gradient composition provided by the present invention,

2 is a diagram showing the absorption spectra of the fibers obtained in Example 1 and Comparative Example 1 of the present invention.

The present invention relates to high-strength inorganic fibers having very good photocatalytic function and methods of making them. In particular, it is related with the inorganic fiber which shows the very outstanding photocatalytic activity by visible light irradiation, and its manufacturing method.

Various attempts have been made to decompose and purify various environmental pollutants using the photocatalytic effect of semiconductors characterized by titanium dioxide. When the photocatalytic effect is used, the titania crystal particles are usually fixed to the substrate. However, various problems arise in the bonding method, and thus, titania fibers that have no problem in immobilization have recently attracted attention.

For example, JP-A-5-184923 discloses a method for synthesizing fibers composed of crystals of anatease titania and vanadium oxide, which dissolve titanium alkoxides and vanadium compounds in alcohol. Performing the hydrolysis to prepare the sol-type material, forming the sol-type material into the fiber-type material, gelling the fiber-type material and gels in the range of 200 to 700 ° C. Heat-treating. The example of JP-A-5-184923 discloses a fiber mainly containing titania and vanadia and further containing a large amount of silica components. Regarding catalytic activity as a fabric using the fiber, JP-A-5-184923 shows only the catalytic activity of a fiber obtained by mixing only 20% of the fiber into an E glass made of silica.

Typically, titania fibers synthesized by the sol-gel method are known to be fragile. As a study for increasing their strength, for example, "Yogyo-Kyokai-shi", vol 94 (12), p 1,243-1,245 (1986) disclose the coexistence of silica components. The method is disclosed in the embodiment of JP-A-5-184923 which uses this method correctly. Furthermore, JP-A-11-5036 discloses a photocatalytic silica-titania fiber according to the sol-gel method and a method for producing the same. In this case, the fiber also has a very low strength of 0.1-1.0 GPa.                         

In addition to the above method, the following report discloses a process for producing titania. For example, "Journal of Material Science Letters" 5 (1986) 402-404 reports a method for the synthesis of gel-type titania fibers (anatates), in which hydrochloric acid coexists in an alcohol solution of titanium alkoxide. Hydrolysis was performed to obtain a colloidal material, the colloidal material was spun and the spun fibers were heated in a humidified atmosphere, followed by temperature-increasing in air to obtain gel-type titania fibers.

Furthermore, in "The American Ceramic Society Bulletin" 1998 5, 61-65, water was added to the fine particles of titania to obtain a slurry, the slurry was mixed with viscose to produce a viscous fluid, and the viscous fluid was It has been reported to form titania fibers by forming the fibers and firing the fibers in air under high temperature heating.

Each fiber is formed through agglomeration of primary particles of titania, thereby causing serious defects inside each fiber. Even if the photocatalytic function is recognized, it is very vulnerable. Therefore, it is required to solve various problems for practical use. Furthermore, in a system in which silica components coexist for the purpose of improving strength, titania and silica are present in a mixed state, whereby sufficient photocatalytic activity is not obtained in comparison with titania alone. This is also an important problem that impedes practical use.

When photocatalytic fibers are used as filters, it is desirable to have higher fiber strength because the photocatalytic fibers are exposed to a high velocity gas stream for a long time. In particular, considering their application to gases emitted from aircraft engines or automobile engines, the development of fibers with high-intensity photocatalytic or thermal-catalytic functions beyond the conventional range is highly desired.

On the other hand, when titania expresses a photocatalytic function, ultraviolet irradiation of 400 nm or less is essential. The spectral distribution of sunlight that can be obtained from the Earth's surface is about 5% in the ultraviolet region (below 400nm), about 43% in the visible region (400-750nm) and about 52% in the infrared region (750nm and above). Therefore, a photocatalyst which expresses a photocatalytic function in the visible light region is preferable in efficiently utilizing sunlight.

As the above method, for example, JP-A-9-192496 discloses a method of doping titanium oxide with metal elements such as V, Cr, Mn, Fe, Co, Ni, Cu, and the like. In the above method, the dopant or a precursor thereof is added to titanium oxide or a precursor thereof, such as a hydroxide, chloride, or nitrate, and dried and calcined to produce a photocatalyst. However, there is a problem that sufficient visible light activity cannot be obtained because it is difficult to introduce the dopant metal in the titanium oxide with uniform and high dispersion.

Furthermore, JP-A-9-262482 discloses a method in which metal ions such as Cr, V, Cu or Fe are accelerated to high energy and irradiated to titanium oxide to introduce metal ions into titanium oxide. According to this method, metal ions can be introduced into the titanium oxide uniformly and with high dispersibility. However, manufacturing costs are very high because large-scale manufacturing equipment is required. Therefore, there is a problem that it is not suitable for mass production.

It is an object of the present invention to provide a high-strength inorganic fiber having excellent photocatalytic activity by visible light irradiation and a method for producing the same.

According to the present invention, silica-based photocatalyst fibers having visible-ray activity are provided, which fibers are composed mainly of an oxide phase (first phase) and a titania phase (second phase) mainly composed of a silica component. A silica-based photocatalyst fiber is provided which comprises an oxide phase, wherein the second phase contains other metal elements than titanium, and the proportion of the second phase is increased slopingly towards the surface of the fiber.

Furthermore, according to the present invention, there is further provided a method for producing silica-based photocatalyst fibers, which

In order to obtain the spun fiber, the modified polycarbosilane having a main chain structure represented by the following formula and obtained by modifying a polycarbosilane having a number average molecular weight of 200 to 10,000 with an organometallic compound is melted. Melt-spinning or

(Wherein R is a hydrogen atom, a lower alkyl group or a phenyl group)                     

Melt-spinning a mixture of the modified polycarbosilane and the organometallic compound;

Insolubilizing the spun fibers; And

Calcining the insoluble fibers in air or oxygen.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The inventors have found that dense high strength silica fibers can be obtained by heat-treating precursor fibers made of organic silicone polymers and then calcining the precursor fibers heat treated in hot air. Then, the inventors of the present invention, when the low molecular weight organometallic compound or the reactant of the low molecular weight organosilicon polymer and the low molecular weight organometallic compound coexist in the organic silicone polymer, the organic metal compound by bleeding in the heat treatment step after spinning The low molecular weight material comprising the component is selectively bleed out to the fiber surface and calcined in air after heat treatment to effectively produce an oxide layer derived from the low molecular weight material (an oxide layer having a desired catalytic function) on the fiber surface. Found. In addition, it has also been found that the fibers obtained according to the method are very dense and have high strength. The step of preparing silica using the organosilicon polymer as a starting material includes an oxidation step of converting a silicon-carbon bond into a silicon-oxygen bond. In this step, its volume is expected to increase by about 1.37 times. This change is achieved at a relatively low temperature of at least 600 ° C., so that by firing, dense silica-based composite fibers are effectively obtained. Thus, it is believed that the above-mentioned high strength is achieved.                     

Furthermore, I found the following: When a compound of a titanium compound and a metal element other than titanium is used as the organometallic compound, the resulting oxide layer is a layer in which a metal other than titanium is uniformly introduced on the titanium with high dispersibility. As a result, it was found that the obtained photocatalyst fiber exhibited excellent visible light activity.

That is, the present invention relates to a silica-based photocatalyst fiber formed of a composite oxide phase comprising an oxide phase (first phase) and a titania phase (second phase) mainly composed of a silica component, wherein the fiber is a second phase. It contains other metal elements other than titanium and is characterized by an increase in the abundance of the second phase towards the surface layer of the fiber.

In the present invention, the oxide phase (first phase) mainly composed of the silica component may be amorphous or crystalline. Furthermore, it may contain metallic elements or metal compounds capable of forming a solid solution or eutectic compound with silica. The metal element (A) capable of forming a solid solution with silica or the metal element (B) capable of forming a compound having a specific structure with silica is not particularly limited, but for example, (A) is titanium And (B) includes aluminum, zirconium, yttrium, lithium, sodium, barium, calcium, boron, zinc, nickel, manganese, magnesium and iron.

The first phase forms the inner phase of the fiber obtained by the present invention, which plays an important role including mechanical properties. The abundance ratio of the first phase relative to the total fibers is preferably 98% by weight to 40% by weight. It is preferable to adjust the abundance ratio of the first phase in the range of 95% by weight to 50% by weight so as to exert high mechanical properties at the same time as the desired second phase.

On the other hand, the titania phase constituting the second phase plays an important role in exhibiting the photocatalytic function intended in the present invention. As for the abundance ratio of the 2nd phase which comprises the surface layer part of the said fiber, 2 to 60 weight% is preferable. It is preferable to adjust the abundance ratio of the second phase in the range of 5 to 50% by weight in order to exhibit sufficient function and at the same time for high strength.

Furthermore, it is essential to contain metal elements other than titanium in the second phase to express visible light activity. As the metal element, at least one metal element selected from Fe, W, Bi, V, Cr, Mn, Co, Ni, Cu, Mg, Ag, Pd, Pt, Zn, Ru, Ce and Rh is used. do. In order to sufficiently exhibit the intended visible light activity, the ratio of metal elements other than titanium in the second phase is preferably 5 to 40% by weight as oxide valency with respect to the entire second phase.

The abundance of the second phase, that is, the abundance of the fine crystal grains that are components of the second phase, increases obliquely toward the fiber surface. It is preferable that the thickness of the region where the composition gradient is clearly recognized is controlled in the range of 5 to 500 nm. The slope region may reach about one third of the fiber diameter. In the present invention, further, each "presence ratio" of the first phase and the second phase refers to all metal oxides constituting the metal oxide constituting the first phase and the metal oxide constituting the second phase, that is, the entire fiber. The "weight%" of the metal oxide of a 1st phase or a metal oxide of a 2nd phase is called.                     

The manufacturing method of the silica-based photocatalyst fiber which has the diagonal structure provided by this invention is demonstrated.

To obtain the spun fiber, melt-spun modified polycarbosilane having a main chain structure represented by the following formula and obtained by modifying a polycarbosilane having a number average molecular weight of 200 to 10,000 with an organometallic compound Or

(Wherein R is a hydrogen atom, a lower alkyl group, preferably a lower alkyl group or phenyl group having 1 to 4 carbon atoms, preferably n is an integer of 1-30.)

The mixture of the modified polycarbosilane and the organometallic compound is melt-spun; Spun fibers are insolubilized; The insolubilized fibers can then be calcined in air or oxygen to produce silica-based photocatalyst fibers.

The first step of the process according to the invention is to prepare a modified polycarbosilane having a number average molecular weight of 1,000 to 50,000 used as a starting material for producing silica-based photocatalyst fibers. The basic manufacturing method of the modified polycarbosilane is very similar to that of JP-A-56-74126. However, in the present invention, it is required to carefully control the binding state of the functional group disclosed in JP-A-56-74126. These general matters are mentioned later.

As a starting material, the modified polycarbosilane has a main chain structure represented by the following chemical formula, and has a number average molecular weight of 200 to 10,000 polycarbosilane and

(Wherein R is a hydrogen atom, a lower alkyl group or a phenyl group)

M (OR ') n or MR "m (wherein M is a metal element, R' is an alkyl or phenyl group having 1 to 20 carbon atoms, R" is acetylacetonate and m and n are each an integer greater than 1) Is preferably an integer greater than 1 and less than 6).

In order to produce fibers having a warp structure provided by the present invention, it is required to select gentle reaction conditions in which only a part of the organometallic compound forms a bond with polycarbosilane. For the above purpose, it is required to carry out the reaction at a temperature of 280 ° C. or lower, preferably 250 ° C. or lower in an inert gas. Under the above reaction conditions, even if the organometallic compound reacts with the polycarbosilane, it binds as a monofunctional polymer (ie, pendant-type bond) and no significant molecular weight increase occurs. The modified polycarbosilane in which the organometallic compound thus obtained is partially bonded plays an important role in improving compatibility between the polycarbosilane and the organometallic compound.

When two or more functional groups are bonded, the polycarbosilane forms a crosslinked structure and a marked increase in molecular weight is observed. In this case, rapid reactions and increased melt viscosity occur during the reaction. On the other hand, when only one functional group is reacted as described above and an unreacted organometallic compound remains, on the contrary, a decrease in melt viscosity is observed.

In the present invention, it is preferable to select reaction conditions such that the unreacted organometallic compound is intentionally left. The present invention mainly uses a substance in which the modified polycarbosilane and an organometallic compound such as an unreacted organometallic compound or a dimer, trimer, and the like coexist. However, when the modified polycarbosilane contains a very low molecular weight modified polycarbosilane component, the modified polycarbosilane can be similarly used alone as a starting material.

In the second step of the method according to the invention, a spinning solution is prepared by melting the modified polycarbosilane or the mixture of the modified polycarbosilane and the low molecular weight organometallic compound obtained in the first step, and spinning in some cases. The solution is filtered to remove harmful substances during spinning, such as microgels or impurities, and the spinning solution is spun onto commonly used synthetic fiber-spinning devices. The temperature of spinning solution during spinning depends on the softening temperature of the modified polycarbosilane, which is a raw material, and it is advantageous to select a temperature range of 50 to 200 ° C. The spinning device may be provided with a humidification and heating cylinder under the nozzle as needed. The diameter of the fiber is adjusted by changing the amount of discharge from the nozzle and the winding speed of the high speed winding unit installed at the bottom of the spinning apparatus. Furthermore, by the melt-blow method or the spin-bonding method, the fiber discharged from the nozzle can be directly formed into a felt shape without winding up.

In addition to the melt-spinning described above, the second step of the process according to the invention takes an example of a modified polycarbosilane or a mixture of a modified polycarbosilane and a low molecular weight organometallic compound obtained in the first step to form a spinning solution. Spinning solutions, for example, to dissolve benzene, toluene, xylene or modified polycarbosilanes and low molecular weight organometallic compounds in a solvent capable of dissolving and, in some cases, to remove harmful substances during spinning such as microgels or impurities The spinning solution can be spun by dry spinning method using a synthetic fiber-spinning device which is generally used, and the winding speed can be controlled to obtain a desired fiber.

In the spinning step, the spinning cylinder can be attached to the spinning device as needed. The atmosphere in the cylinder is replaced with a mixed atmosphere mixed with at least one gas selected from the above solvents or with an atmosphere of air, inert gas, heated air, heated inert gas, steam, ammonia gas, hydrocarbon gas or organosilicon compound gas. And thus solidification of the fibers in the spinning cylinder can be controlled.

Thereafter, in the third step of the method of the present invention, the spun fiber is preheated with or without tension in the oxidizing atmosphere to insolubilize the spun fiber. The purpose of this step is to prevent the fibers from melting in the post-firing step and to prevent adjacent fibers from adhering to each other. Treatment temperature and treatment time depend on the composition. Although not particularly limited, it is generally treated in the range of 50 to 400 ° C. for several hours to 30 hours. The oxidizing atmosphere may contain a substance that increases the oxidation strength of spinning fibers such as moisture, nitrogen oxides, and ozone, and the oxygen partial pressure may be intentionally changed.                     

In some cases, depending on the proportion of low molecular weight substances in the raw materials, the softening point temperature of the spun fibers may be less than 50 ° C. In this case, the treatment which promotes oxidation of the fiber surface is performed in advance in some cases at a temperature lower than the treatment temperature. In the third and second stages, the low molecular weight organometallic compounds contained in the raw material are first bleed out to the fiber surface. It is thus believed that a ground of the desired gradient composition is formed.

In the fourth step of the method of the present invention, the insoluble fibers are subjected to an oxide phase mainly composed of silica by firing in an oxidizing atmosphere at a temperature range of 500 to 1,800 ° C with or without tension. A composite oxide phase comprising a first phase) and a titania phase (second phase) is formed, wherein the second phase contains other metal elements than titanium, and the abundance of the second phase increases obliquely toward the surface layer of the fiber. Silica-based photocatalyst fibers are obtained. In this step, the organic components contained in the insoluble fiber are basically oxidized. However, in some cases, the organic component may remain in the fiber as carbon or carbide depending on the conditions chosen. Even in such a case, it is used as long as it does not interfere with the desired function, but in the case of causing a problem, further oxidation treatment is performed. In such a case, it is required to select a temperature and a treatment time which do not cause problems with the desired gradient composition and the desired crystal structure.

1 shows the step of producing an oxide fiber having the desired gradient composition provided by the present invention.                     

Example

The invention is explained in more detail by way of examples.

Reference Example 1

2.5 liters of anhydrous toluene and 400 g of metal sodium were charged into a 5 liter 3-necked flask, the mixture was heated to the boiling point of toluene under a stream of nitrogen gas and 1 liter of dimethyldichlorosilane was added dropwise over 1 hour. After the addition was completed, the mixture was heated to reflux for 10 hours to obtain a precipitate. The precipitate was collected by filtration, washed with methanol and then washed with water to give 420 g of a white powder of polydimethylsilane.

250 g of polydimethylsilane was charged to a three-necked flask equipped with a water cooling reflux device and heated at 420 ° C. for 30 hours under a nitrogen gas stream to obtain a polycarbosilane having a number average molecular weight of 1,200.

Example 1

100 g of toluene, 50 g of tetrabutoxytitanium, and 5 g of iron (III) acetylacetonate were added to 50 g of polycarbosilane synthesized according to Reference Example 1, and the mixture was preheated at 100 ° C. for 1 hour, and then the mixture was 150 The toluene was distilled off slowly by increasing the temperature to 0 ° C., and the resultant mixture was reacted at this temperature for 5 hours, and then the reaction mixture was further heated to 250 ° C. and reacted at this temperature for 5 hours to obtain a modified polycarbosilane. Tetrabutoxytitanium 5g was added to the modified polycarbosilane for the purpose of intentionally coexisting the low molecular weight organometallic compound to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound.

The mixture of the modified polycarbosilane and the low molecular weight organometallic compound is dissolved in toluene, the resulting solution is charged into a spinning apparatus made of glass, nitrogen-substituted sufficiently and the temperature is raised to distill off the toluene, and the resultant is heated at 180 ° C. Melt spun.

The spun fibers were heated stepwise to 150 ° C. in air to form insoluble fibers and calcined at 1,200 ° C. for 1 hour in air to obtain silica-based photocatalyst fibers.

The obtained fiber (average diameter: 13 µm) was analyzed for the content of each element by using fluorescent X-rays. In terms of oxide value, the amount of silica was 80% by weight, the amount of titania was 17% by weight, and the amount of iron oxide was 3% by weight. Further, the fibers were examined for the dispersion state of constituent atoms by EPMA (electron probe microanalysis). The molar ratio of Ti / Si is 0.87 in the region from the outermost periphery to 1 µm deep, and the molar ratio of Ti / Si is 0.15 in the region 3 to 4 µm deep from the outermost periphery. The molar ratio was 0.04. Thus, the fiber was found to have a tilting composition with increasing titanium towards the surface. Similarly, the molar ratio of Fe / Si in the region from the outermost circumference to 1 탆 depth is 0.08, the molar ratio of Fe / Si in the region of 3 to 4 탆 depth from the outermost circumference is 0.02, and the Fe in the central portion is Fe. The molar ratio of / Si was 0.01. Therefore, it was confirmed that the fiber has a gradient composition in which iron increases toward the surface. The fiber had a tensile strength of 1.7 GPa. The tensile strength of the fibers was significantly greater than that of the anateis titania / silica fibers obtained by the conventional sol-gel method.

Furthermore, the absorption spectrum of the fiber was measured and the results are shown in FIG.

0.2 g of the fiber was placed in a 60 mm diameter curry. 20 milliliters of water with 1,000,000 coliforms per milliliter was added to the curry. The water was irradiated with a xenon lamp equipped with a filter for cutting light having a wavelength of 420 nm or less from the top of the saree for 24 hours. After irradiation, E. coli solution was taken from the sare and incubated in agar medium. Thereafter, the number of residual E. coli was examined. The number of residual E. coli was zero. Photocatalytic activity by visible light irradiation was confirmed.

Example 2

100 g of toluene, 50 g of tetrabutoxytitanium and 3 g of tungsten ethoxide were added to 50 g of polycarbosilane synthesized according to Reference Example 1, the mixture was preheated to 100 ° C. for 1 hour, and then the mixture was slowly heated to 150 ° C. Toluene was distilled off, and the resulting mixture was reacted at this temperature for 5 hours, and then the reaction mixture was heated up to 250 ° C. and reacted at this temperature for 5 hours to obtain a modified polycarbosilane. In order to coexist the intended low molecular weight organometallic compound, 5 g of tetrabutoxytitanium was added to the modified polycarbosilane to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound.

The mixture of the modified polycarbosilane and the low molecular weight organometallic compound is dissolved in toluene, the resultant mixture is charged into a spinning apparatus made of glass, nitrogen-substituted and warmed up, and the toluene is distilled off, and the resulting material is at 180 ° C. Melt-spun.

Spinning fibers were heated stepwise to 150 ° C. in air to form insoluble fibers, and the insoluble fibers were calcined for 1 hour in 1,200 ° C. air to obtain silica-based photocatalyst fibers.

The obtained fiber (diameter: 13 micrometers) analyzed the ratio which contained each element using the fluorescent X-ray. The amount of silica in terms of oxide was 80% by weight, the amount of titania was 15% by weight, and the amount of tungsten oxide was 5% by weight. Further, the fibers were examined for the dispersion state of the members by EPMA. The molar ratio of Ti / Si is 0.85 in the region of 1 µm deep from the outermost periphery, and the molar ratio of Ti / Si is 0.13 in the region of 3-4 µm deep from the outermost periphery. 0.04. Therefore, it was confirmed that the fiber had an inclined composition in which titanium was increased toward the surface. Similarly, the molar ratio of W / Si is 0.07 in the region of 1 탆 depth from the outermost circumference, the molar ratio of W / Si is 0.02 in the region of 3-4 탆 depth from the outermost circumference, and W / Si in the region of the central portion. The molar ratio of Si was 0.01. Therefore, it was confirmed that the fiber had an inclined composition in which tungsten was increased toward the surface. The fiber had a tensile strength of 1.6 GPa. The tensile strength of the fibers was significantly greater than that of the enanthate titania / silica obtained by the conventional sol-gel method.

0.2 g of the fiber was placed in a 60 mm diameter curry. 20 milliliters of water with 1,000,000 coliforms per milliliter was added to the curry. The water was irradiated for 24 hours with a xenon lamp equipped with a filter that cuts light having a wavelength of 420 nm or less from the top of the saree. After irradiation, E. coli solution was taken from the sare and incubated in agar medium. Thereafter, the number of residual E. coli was examined. The number of residual E. coli was zero. Photocatalytic activity by visible light irradiation was confirmed.

Comparative Example 1

100 g of toluene and 50 g of tetrabutoxytitanium were added to 50 g of polycarbosilane synthesized according to Reference Example 1, the mixture was preheated at 100 ° C for 1 hour, and then the mixture was slowly heated to 150 ° C to distill off the toluene. The resulting mixture was allowed to react at this temperature for 5 hours, and then the reaction mixture was heated up to 250 ° C. and reacted at this temperature for 5 hours to obtain modified polycarbosilane. Tetrabutoxytitanium 5g was added to the polycarbosilane for the purpose of intentionally coexisting the low molecular weight organometallic compound to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound.

The mixture of the modified polycarbosilane and the low molecular weight organometallic compound is dissolved in toluene, the resulting solution is charged into a spinning machine made of glass, nitrogen-substituted sufficiently and the temperature is raised to distill off the toluene, and the resultant is 180 ° C. Melt-spinning.

The spinning fibers were gradually heated to 150 ° C. in air to form insoluble fibers, and the insoluble fibers were calcined at 1,200 ° C. in air for 1 hour to obtain titania / silica fibers.

The obtained fiber (average diameter: 13 µm) was analyzed for the content of each element by using fluorescent X-rays. In terms of oxide valency, the amount of silica was 83% by weight and the amount of titania was 17% by weight. Furthermore, the fibers were examined for dispersion state of constituent atoms with EPMA. The molar ratio of Ti / Si is 0.85 in the region of 1 μm deep from the outermost periphery, and the molar ratio of Ti / Si is 0.13 in the region of 3-4 μm deep from the outermost periphery. 0.04. Therefore, it was confirmed that the titanium has a gradient composition toward the surface. The fiber had a tensile strength of 1.8 GPa. The tensile strength of the fibers was significantly higher than that of the enanthate titania / silica obtained by the conventional sol-gel method.

Furthermore, the absorption spectrum of the fiber was measured and the results are shown in FIG.

0.2 g of the fiber was placed in a 60 mm diameter curry. 20 milliliters of water with 1,000,000 coliforms per milliliter was added to the curry. The water was irradiated with a xenon lamp equipped with a filter for cutting light having a wavelength of 420 nm or less from the top of the saree for 24 hours. After irradiation, E. coli solution was taken from the sare and incubated in agar medium. Thereafter, the number of residual E. coli was examined. It was found that the number of E. coli increased to 100,000,000. Photocatalytic activity by visible light irradiation was not confirmed.

The silica-based photocatalyst fibers of the present invention have good visible light activity.

Claims (6)

A composite oxide comprising an oxide phase (first phase) and a titania phase (second phase) mainly composed of a silica component, wherein the second phase contains a metal element other than titanium, and an abundance ratio of the second phase A silica-based photocatalyst fiber having visible light activity that increases obliquely toward the surface of silver fibers. The silica-based photocatalyst fiber according to claim 1, wherein the proportion of the first phase to the fiber is 98 to 40% by weight, and the proportion of the second phase to the fiber is 2 to 60% by weight. 3. The silica-based photocatalyst fiber according to claim 2, wherein the abundance ratio of metal elements other than titanium in the second phase is 5 to 40% by weight in terms of oxide relative to the entire second phase. The metal phase of claim 1 wherein the metal elements other than titanium in the second phase are Fe, W, Bi, V, Cr, Mn, Co, Ni, Cu, Mg, Ag, Pd, Pt, Zn, Ru, Ce, and Rh. Silica-based photocatalyst fibers, characterized in that at least one metal element selected from the group consisting of. In order to obtain the spun fiber, the modified polycarbosilane having a main chain structure represented by the following formula and obtained by modifying a polycarbosilane having a number average molecular weight of 200 to 10,000 with an organometallic compound, or

(Wherein R is a hydrogen atom, a lower alkyl group or a phenyl group) Melt-spinning a mixture of the modified polycarbosilane and the organometallic compound; Insolubilizing the spun fibers; And Calcining the fibers insolubilized in air or in oxygen; Method for producing a silica-based photocatalyst fiber of claim 1 comprising a. The method of claim 5, wherein the organometallic compound is a compound having a basic structure of the formula M (OR ') n' or MR "m, wherein M is Fe, W, Bi, V, Cr, Mn, Co, Ni, At least one metal element selected from the group consisting of Cu, Mg, Ag, Pd, Pt, Zn, Ru, Ce, and Rh, R 'is an alkyl or phenyl group having from 1 to 20 carbon atoms, and R "is acetyl Acetonate, wherein m and n 'are integers greater than 1 and less than 6, respectively.

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